Pseudorhabdosynochus manifestus, Justine, Jean-Lou & Sigura, Aude, 2007

Justine, Jean-Lou & Sigura, Aude, 2007, Monogeneans of the malabar grouper Epinephelus malabaricus (Perciformes, Serranidae) off New Caledonia, with a description of six new species of Pseudorhabdosynochus (Monogenea: Diplectanidae), Zootaxa 1543, pp. 1-44 : 6-11

Pseudorhabdosynochus manifestus n. sp.

( Figs 2–5 )

Type host: Epinephelus malabaricus Bloch & Schneider (Serranidae) .

Type locality: Lagoon off Nouméa, New Caledonia.

Site: Between secondary gill lamellae.

Type specimens: Holotype, JNC 1536A26, off Ouen Toro, Nouméa, New Caledonia (22°19'S, 166°27'E, 18.v.2005).

Material examined: 220 specimens: 129 ‘carmine’ (c), 91 ‘picrate’ (p).

Material deposited: Holotype (c) and 204 paratypes (113 c, 91 p), MNHN; for all other collections, 3 paratypes (c) including 1 from fish JNC 1536 and 2 from fish JNC 2130: BMNH 2007.6.1.1—3; USNPC 99867—8; SAMA AHC 29213-4; HCIP M-440; SLZU ZSU 20070613-1-1—3.

Prevalence: 100% (2/2). The only species which was found in the two fish examined.

Intensity: See Table 1. Maximum intensity for both gill sides evaluated to several hundreds. This species was the dominant species in both fish, and represented 65–80% of the diplectanids (65–66% of the monogeneans).

Etymology: From ‘ manifestus’ (Latin), clear, evident, refers to the fact that this was the most abundant species.

Description: Body elongate; length h 670, c 665±85 (450–870, n = 29), width h 290, c 306±50 (170–410, n = 30). Tegument scaly; posterior region with scales on ventral and dorsal faces from squamodiscs to level of ovary and testis. Anterior region with 3 pairs of head organs and 2 pairs of eye-spots; distance between outer margins of anterior eye-spot pair h 43, c 46±11.6 (31–70, n = 30), of posterior eye-spot pair h 44, c 44±8.9 (28–65, n = 30).

Haptor differentiated from rest of body, less wide than body, width 220, c 247±26 (190–300, n = 28), provided with 2 similar squamodiscs, 2 pairs of lateral hamuli, 3 bars and 14 marginal hooklets. Squamodiscs round in shape, made up of rows of rodlets; central rows forming almost closed ovals; rodlets progressively thinner from centre to periphery; rodlets adjacent in all rows except last row; last row with very thin, separated rodlets; ventral and dorsal squamodiscs similar, but ventral slightly larger; ventral squamodisc length h 63, c 60 (53–67, n = 18), width h 65, c 61 (54–70, n = 18), with 10–11 (n = 18) rows of rodlets and 0–2 closed ovals; total number of rodlets h 87; dorsal squamodisc, length h 54, c 54 (48–62, n = 19), width h 57, c 56 (50–62, n = 20), with 10–12 (n = 20) rows of rodlets and 0–2 closed ovals; total number of rodlets h 86. Ventral hamulus with thick handle and distinct guard, outer length h 57, c 57±2.5 (53–62, n = 59), p 59±1.9 (55– 62, n = 64), inner length h 48, c 49±2.1 (44–53, n = 59), p 47±1.2 (44–51, n = 64). Dorsal hamulus with indistinct guard, outer length h 50, c 48±1.6 (44–52, n = 64), p 48±1.3, (45–52, n = 64), inner length h 31, c 30±1.0 (27–33, n = 64), p 30±1.1 (28–34, n = 64). Dorsal (lateral) bars straight, with flattened medial extremity and thick cylindrical lateral extremity, length h 83, c 84±3.7 (74–90, n = 64), p 87±4.5 (79–99, n = 64), maximum width h 27, c 26±2.2 (20–31, n = 62), p 27±2.4 (21–33, n = 64). Ventral bar flat, massive, with slightly constricted median portion and blunt extremities, length h 114, c 117±4.1 (108–126, n = 31), p 118±5.2 (108–128, n = 32), maximum width h 23, c 23±2.3 (16–27, n = 30), p 24±2.6 (20–34, n = 32); groove visible on its ventral side.

Pharynx subspherical, length h 50, c 56±7.8 (35–70, n = 32), width h 44, c 46±5.1 (35–58, n = 32). Oesophagus apparently absent, such that intestinal bifurcation immediately follows pharynx. Caeca simple, terminate blindly at level of posterior margin of vitelline field.

Testis subspherical, intercaecal, length h 70, c 58 (35–75, n = 22), width h 50, c 66 (35–126, n = 22). Vas deferens emerges from antero-sinistral part of testis, enlarges into seminal vesicle; seminal vesicle in middle region of body, transforms into duct; duct forms bends then connects with quadriloculate organ; terminal portion of duct enlarged. Prostatic reservoir small, connects with quadriloculate organ. Quadriloculate organ with fourth (posterior) chamber slightly more sclerotised than 3 anterior chambers; fourth chamber ends in elongate sclerotised cone, prolonged by sclerotised tube; end of tube prolonged by thin unsclerotised filament of variable length. Inner length of quadriloculate organ h 51, c 57±2.6 (50–60, n = 31), p 70±6.3 (58–83, n = 33); cone length h 20, c 19±1.6 (17–23, n = 31), p 20±3.0 (15–32, n = 33); tube length h 23, c 22±1.6 (18–25, n = 29), p 21±2.3 (18–28, n = 30); tube diameter h 3, c 3.0±0.5 (3–4, n = 31), p 3.0±0.6 (3–4, n = 30); filament length h 47, c 0–48 (n = 28), p 0–45 (n = 30).

Ovary subequatorial, intercaecal, pre-testicular, encircles right caecum. Ovary width h 80, c 89 (65–115, n = 24). Oviduct passes medially to form oötype, surrounded by Mehlis’ gland; oötype short, opens into uterus. Uterus dextral. Unsclerotised vagina often inconspicuous, elongate ( Figure 3 U,V). Duct from sclerotised vagina to oötype inconspicuous. Vitelline fields extend posteriorly from posterior to pharyngeal level in 2 lateral bands, confluent in post-testicular region and terminate anterior to peduncle. Bilateral connections from vitelline fields to oötype inconspicuous. Egg in utero oval, 103 (90–115) × 41 (28–54) (n = 4), with long filament.

Sclerotised vagina (nomenclature of parts according to Justine 2007a; see Figure 20 ). Sinistral, a complex sclerotised structure; aspect changes according to specimen and orientation ( Figure 3 ). General shape resembling a “?” in dorsal view ( Figure 3 A–C). Sclerotised vagina comprises anterior trumpet, followed by primary canal, primary chamber and secondary chamber; trumpet in continuity with unsclerotised vagina; primary canal cone-shaped, coiled in its anterior part and straight in its posterior part; wall of anterior part thin, wall of posterior part thicker with distinct ring often visible at mid-length; canal continues into primary chamber; primary chamber roughly spherical, aligned and in continuity with primary canal, more sclerotised and larger than it; thin longitudinal median wall in primary chamber, inserted posteriorly, visible in certain specimens ( Figure 3 A, B, I, M, Q, V, X); secondary canal inserted laterally on primary chamber; secondary chamber sclerotised, elongate, lateral to primary chamber; accessory structure, weakly sclerotised, inserted on secondary chamber and directed anteriorly. Duct from sclerotised vagina to oötype connects to secondary chamber ( Figure 3 J,V). Total length of sclerotised vagina (measured from extremity of trumpet to extremity of primary chamber, i.e. not taking in account curved length along bend and coil of canal) h 35, c 34±1.6 (31–38, n = 32), p 33±3.2 (25–38, n = 33). Orientation of sclerotised vagina: trumpet always anterior.

Differential diagnosis. Three species, Pseudorhabdosynochus huitoe Justine, 2007 from E. maculatus off New Caledonia, and P. shenzhenensis Yang, Zeng & Gibson, 2005 , P. serrani ( Yamaguti, 1953) Kritsky & Beverley-Burton, 1986 (in its redescription by Yang et al. 2005), both from E. coioides off China share with P. manifestus the following characteristics of the sclerotised vagina: a conical primary canal (wider at the anterior part), with a single coil in its anterior part and a straight posterior part, and small primary and secondary chambers/( Table 2 ).

P. huitoe shares additional characteristics of the vagina with P. manifestus : a spherical primary chamber with thin longitudinal internal wall, and an elongate secondary chamber with distinct secondary canal. P. manifestus can be differentiated from this species by the posterior part of the primary canal, thick with distinct ring vs thin without ring, and longer vagina, 34 vs 25. Similarities also include ventral bar length, dorsal bar length, and a quadriloculate organ with long cone and long tube; however, measurements of the quadriloculate organ, ventral hamuli and dorsal hamuli are distinctly greater in P. manifestus . Clearly, these two species are very similar but can be distinguished on the basis of vagina structure and various measurements.

P. shenzhenensis and P. serrani also have a vagina with a primary canal coiled in its anterior part and a grossly similar shape of the chambers. In P. serrani , the measurements of dorsal and ventral bars are very similar to P. manifestus , but the species can be differentiated by measurements of ventral hamuli, dorsal hamuli, and quadriloculate organ which are distinctly greater in P. manifestus . P. shenzhenensis is easily differentiated from the three other species by its shorter ventral bar. Examination of specimens shows that the posterior part of the primary canal, in P. shenzhenensis and P. s e r r a n i do not show the distinctive ring of P. m a n i f e s t u s, and the shapes of chambers are different. The tegumental scales might be an additional useful distinctive character.

Remarks on a juvenile specimen ( Figure 5 ). Among the large number of specimens collected, several juvenile specimens were observed. We report observations on a specimen in which the sclerotised vagina was already fully formed, thus allowing identification of the species. Proportions of the body were very different from the adult, with a comparatively wider haptor ( Figure 5 A). Measurements were: body length 410 (61% of adult mean), width 100 (33%), haptor width 190 (77%). Sclerotised organs all showed measurements ranging 75–84% of their adult equivalents: ventral hamuli outer length 48, inner length 40, dorsal hamuli outer length 40, inner length 24, lateral bar length 64, ventral bar length 101, ventral squamodisc width 47, dorsal squamodisc width 43. Although growth of the male quadriloculate organ (inner length 57, 79% of adult mean) and sclerotised vagina (length 28, 82%) were similar in proportions, the development of these two organs was different. The sclerotised vagina was perfectly similar to an adult organ. The quadriloculate organ was very different, with more elongate general shape, thinner external walls, and the cone and tube were indistinguishable. The ovary was visible, but not the testis. These observations show that development of female organs precedes that of male organs in this species, and probably in other species of Pseudorhabdosynochus .

Measurements indicated are means from carmine specimens; * These measurements were misprinted in the text of the original description ( Justine, 2007a p. 112) but were correct in the comparative Table (p. 113). ** confirmed by examination of voucher.

Figures

FIGURE 2. Pseudorhabdosynochus manifestus n. sp. A. Composite drawing; tegumental scales drawn only on edges. B. Quadriloculate organ. C. Sclerotised vagina. B, C, holotype; A – C, ventral view, carmine.

FIGURE 3. Pseudorhabdosynochus manifestus n. sp. Sclerotised vagina, variation according to specimen, orientation and fixation method. Note general shape reminding a “? ”, particularly in A – C. A – M, carmine, dorsal view; N – T, carmine, ventral view; U – Y, picrate, dorsal view; Z, picrate, ventral view. All paratypes.

FIGURE 4. Pseudorhabdosynochus manifestus n. sp. A. Ventral squamodisc, ventral view. B. Dorsal squamodisc, same individual, ventral view. C. Tegumental scales. D. Ventral bar. E. Dorsal bar. F. Ventral hamulus. G. Dorsal hamulus. A – C, holotype, carmine; D – G, paratype, picrate.

FIGURE 5. Pseudorhabdosynochus manifestus n. sp., development of sclerotised copulatory organ in a juvenile. A. Silhouette of body. B. Quadriloculate organ. C. Sclerotised vagina. Dorsal view, carmine.

FIGURE 20. Pseudorhabdosynochus spp: nomenclature and measurements (italics) of sclerotised vaginae. Abbreviations as in general diagram. P. s e r r a n i (voucher from E. coioides, MNHN JNA 6 A 1) drawn for comparison with P. m a n i - festus; P. shenzhenensis (voucher from E. coioides, MNHN JNA 5 A 1) drawn for comparison with specimens from E. malabaricus. pcid, primary chamber internal diameter; pced, primary chamber external diameter; scid, secondary chamber internal diameter; sced, secondary chamber external diameter.

Tables

TABLE 2. Selected measurements and abbreviated vagina characteristics for three species resembling P. m a n i f e s t u s and P. m a a e n s i s. From Yang et al. (2005) and Justine (2007 a).

Characteristic	P. huitoe	P. shenzhenensis	P. serrani	P. manifestus n. sp.	P. m a a e n s i s n. sp.
Body Length	440	314–519	434	665	498
Dorsal Bar Length	84	72	79	84	51
Ventral Bar Length	119	81	113	117	79
Ventral Hamulus Outer Length	45 *	41	42	57	42
Dorsal Hamulus Outer Length	37 *	33	34	48	39
Ventral Squamodisc Diameter	50	43	52–63	60	44
Dorsal Squamodisc Diameter	49	40	52	55	40
Squamodisc Rows	9–12	9–11	9–11	10–12	10–13
Quadriloculate Organ Internal Length	45	43	28	57	34
Vagina Length	25	30 (16 in voucher)	39 (26 in voucher)	34	43
Vagina Primary Canal	conical	conical	conical	conical	cylindrical
Vagina Primary Canal Wall	thin	thin	without ring	with ring	thin
Tegumental scales	Posterior region	Only on pedun- cle **	Only on peduncle	Posterior region	Posterior region